Most motor vehicles are equipped with an internal combustion engine, which is generally used for driving the vehicle. An internal combustion engine of this type has a crankcase, preferably if it is designed as a piston engine. A crankshaft is located in the crankcase, which is connected via connecting rods to pistons of the individual cylinders of the internal combustion engine. Leaks between the piston and the associated cylinder walls lead to a blow-by gas flow, by means of which, blow-by gas reaches the crankcase from the combustion chambers. To prevent an unpermitted overpressure in the crankcase, modern internal combustion engines are equipped with a crankcase ventilation apparatus, in order to dissipate the blow-by gases from the crankcase.
To reduce hazardous emissions, the blow-by gas is conventionally fed with the aid of the crankcase ventilation apparatus to a fresh air system of the internal combustion engine, which supplies the combustion chambers of the internal combustion engine with fresh air. An oil mist prevails in the crankcase, so that the blow-by gas conveys oil with it. This oil may, as oil droplets, damage elements in the intake tract, such as a turbocharger, for example. In order to protect these elements and to reduce the oil consumption, the crankcase ventilation apparatus conventionally has an oil-separating apparatus and preferably an oil return, which returns the separated oil to the crankcase.
In the case of crankcase ventilation apparatuses, passive systems can be differentiated fundamentally from active systems. Passive systems use the pressure difference between the crankcase and the underpressure in the fresh air system for driving the blow-by gas. Active systems additionally generate an underpressure for exhausting the blow-by gas out of the crankcase. As a result, a higher pressure difference can be used in the oil separation, so that the separation is improved. In supercharged internal combustion engines, for example by means of a compressor or turbocharger, it is known to use an ejector pump, which is driven by the compressed air of the supercharging apparatus and therefore generates an underpressure, with the aid of which a higher differential pressure can be generated.
In exhaust turbochargers in particular, the responsiveness of the internal combustion engine can be reduced considerably in the case of partial load or idling as a result, because energy is removed in the supercharging apparatus when there is only little energy present anyway owing to the low power of the engine.
A crankcase ventilation apparatus is for example known from WO 2013/017832 A1, in which an underpressure is generated for ventilating the crankcase by means of an ejector pump. In this case, the ejector pump is driven by compressed air from a turbocharger.